DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0089; Project Identifier 2019-NM-159-AD]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Proposed rule; withdrawal.

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SUMMARY: The FAA is withdrawing a notice of proposed rulemaking (NPRM)
that proposed to adopt a new airworthiness directive (AD). That NPRM
would have applied to certain The Boeing Company Model 737-700, -800,
and -900ER series airplanes. The NPRM was prompted by a report of
unshimmed gaps at a certain frame inner chord. The NPRM would have
required a general visual inspection for repairs of a certain frame
inner chord, a detailed inspection for unshimmed gaps of the frame
inner chord, and applicable on-condition actions. Since issuance of the
NPRM, the FAA determined that the proposed AD is inadequate to address
the unsafe condition. The FAA intends to propose new rulemaking to
incorporate changes to the proposed requirements and add airplanes that
are also subject to the unsafe condition. Accordingly, the NPRM is
withdrawn.

DATES: The FAA is withdrawing the proposed rule published on February
4, 2020 (85 FR 6107), as of June 24, 2021.

ADDRESSES:

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2020-0089;
or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
this AD action, any comments received, and other information. The
street address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Greg Rutar, Aerospace Engineer,
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3529; email:
Greg.Rutar@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued an NPRM that proposed to amend 14 CFR part 39 by
adding an AD that would apply to certain Boeing Model 737-700, -800,
and -900ER series airplanes. The NPRM was published in the Federal
Register on February 4, 2020 (85 FR 6107). The NPRM was prompted by a
report of unshimmed gaps at a certain frame inner chord.

The NPRM proposed to require a general visual inspection for
repairs of a certain frame inner chord, a detailed inspection for
unshimmed gaps of the frame inner chord, and applicable on-condition
actions. The proposed actions were intended to address gaps at a frame
inner chord, which may initiate early cracking in fatigue critical
baseline structure (FCBS) and result in the inability of a principal
structural element (PSE) to sustain limit load and adversely affect the
structural integrity of the airplane.

Actions Since the NPRM Was Issued

Since issuance of the NPRM, the FAA determined that the proposed
actions are inadequate to address the unsafe condition. In addition to
identifying missing shims, Boeing has found a wrong type of shims,
shanked fasteners, fastener head gaps, and incorrect fastener hole
sizes. The unsafe condition and location of the problem are the same as
those described in the NPRM. The FAA has identified additional Model
737-700, -800, and -900ER airplanes as well as additional airplane
models that are subject to the unsafe condition. The FAA has also
determined that additional actions must be accomplished to address the
unsafe condition on the affected airplanes. In light of these changes,
the FAA intends to propose further rulemaking.

Withdrawal of the NPRM constitutes only such action. The withdrawal
does not preclude the FAA from further rulemaking on this issue or
commit the FAA to any course of action in the future.

Comments

The FAA received comments on the NPRM from four commenters,
including Aviation Partners Boeing, Boeing, Delta Air Lines, and United
Airlines. Although the FAA is withdrawing the NPRM because of new
findings and not as a result of any of these comments, the following
presents a brief discussion of the comments.

United Airlines concurred with the NPRM.

Aviation Partners Boeing and Delta Air Lines stated that the
incorporation of supplemental type certificate (STC) ST00830SE for in-
stallation of blended or split scimitar winglets does not affect compli-
ance with the proposed actions, so a "change in product" alternative
method of compliance (AMOC) would not be necessary. The FAA agrees with
the commenters' assertions, but because the FAA is withdrawing the NPRM,
the request is no longer necessary.

Delta Air Lines noted that the service information recommended
removing sealant squeeze-out that inhibits inserting the feeler gauge
between the mating surfaces. The commenter was concerned that removing
the sealant squeeze-out could damage the structure if a metallic tool
is used. The FAA disagrees with the request; however, because the NPRM
is being withdrawn, the commenter's requested change is unnecessary.

Boeing requested several changes to the Discussion and Related
Service Information Under 1 CFR part 51 sections and the description of
the unsafe condition in the NPRM. The FAA disagrees with Boeing's
requested changes. However, because the NPRM is being withdrawn, the
commenter's requested changes are unnecessary.

FAA's Conclusions

Upon further consideration, the FAA has determined that the NPRM
does not adequately address the identified unsafe condition.
Accordingly, the FAA is withdrawing the NPRM.

Regulatory Findings

Since this action only withdraws an NPRM, it is neither a proposed
nor a final rule. This action therefore is not covered under Executive
Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference,
Safety.